Abstract

Rabeprazole is oxidized by hexacyanoferrate(III) and the kinetics of oxidation has been studied spectrophotometrically. The reaction exhibits 1:1 stoichiometry. The reaction rate shows first-order with respect to [HCF], [Cu] and fractional order with respect to [RAB]. Temperature effect on reaction rate was studied. Different activation parameters Ea (kJ/mol-1), ΔH# (kJmol-1), ΔS#(JK-1mol-1) and ΔG# (kJmol-1) with respect to the slow step of the mechanism are computed and tabulated. Effect of ionic strength and dielectric constant of medium has been studied. Rate constant for rate determining step was calculated and a suitable mechanism has been proposed. Hydrated Cu-HCF complex reacts with rabeprazole sodium which forms an intermediate complex which dissociates to form products rabeprazole sulphone. The rate law was derived as Rate=kK2[RABNa][ Cu-HCF]T/ K1+K2[RAB-Na].

Authors and Affiliations